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CVE-2023-48795

Publication date 18 December 2023

Last updated 2 October 2024

Ubuntu priority

Medium

Why this priority?

Cvss 3 Severity Score

5.9 · Medium

Score breakdown

The SSH transport protocol with certain OpenSSH extensions, found in OpenSSH before 9.6 and other products, allows remote attackers to bypass integrity checks such that some packets are omitted (from the extension negotiation message), and a client and server may consequently end up with a connection for which some security features have been downgraded or disabled, aka a Terrapin attack. This occurs because the SSH Binary Packet Protocol (BPP), implemented by these extensions, mishandles the handshake phase and mishandles use of sequence numbers. For example, there is an effective attack against SSH's use of ChaCha20-Poly1305 (and CBC with Encrypt-then-MAC). The bypass occurs in chacha20-poly1305@openssh.com and (if CBC is used) the -etm@openssh.com MAC algorithms. This also affects Maverick Synergy Java SSH API before 3.1.0-SNAPSHOT, Dropbear through 2022.83, Ssh before 5.1.1 in Erlang/OTP, PuTTY before 0.80, AsyncSSH before 2.14.2, golang.org/x/crypto before 0.17.0, libssh before 0.10.6, libssh2 through 1.11.0, Thorn Tech SFTP Gateway before 3.4.6, Tera Term before 5.1, Paramiko before 3.4.0, jsch before 0.2.15, SFTPGo before 2.5.6, Netgate pfSense Plus through 23.09.1, Netgate pfSense CE through 2.7.2, HPN-SSH through 18.2.0, ProFTPD before 1.3.8b (and before 1.3.9rc2), ORYX CycloneSSH before 2.3.4, NetSarang XShell 7 before Build 0144, CrushFTP before 10.6.0, ConnectBot SSH library before 2.2.22, Apache MINA sshd through 2.11.0, sshj through 0.37.0, TinySSH through 20230101, trilead-ssh2 6401, LANCOM LCOS and LANconfig, FileZilla before 3.66.4, Nova before 11.8, PKIX-SSH before 14.4, SecureCRT before 9.4.3, Transmit5 before 5.10.4, Win32-OpenSSH before 9.5.0.0p1-Beta, WinSCP before 6.2.2, Bitvise SSH Server before 9.32, Bitvise SSH Client before 9.33, KiTTY through 0.76.1.13, the net-ssh gem 7.2.0 for Ruby, the mscdex ssh2 module before 1.15.0 for Node.js, the thrussh library before 0.35.1 for Rust, and the Russh crate before 0.40.2 for Rust.

Read the notes from the security team

Status

Package Ubuntu Release Status
dropbear 24.10 oracular
Needs evaluation
24.04 LTS noble
Needs evaluation
23.10 mantic Ignored end of life, was needs-triage
23.04 lunar Ignored end of life, was needs-triage
22.04 LTS jammy
Needs evaluation
20.04 LTS focal
Needs evaluation
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial
Needs evaluation
14.04 LTS trusty Ignored end of standard support
filezilla 24.10 oracular
Fixed 3.66.4-1
24.04 LTS noble
Fixed 3.66.4-1
23.10 mantic
Fixed 3.65.0-3ubuntu0.1
23.04 lunar Ignored end of life, was needed
22.04 LTS jammy
Fixed 3.58.0-1ubuntu0.1
20.04 LTS focal
Fixed 3.46.3-1ubuntu0.1
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty Not in release
golang-go.crypto 24.10 oracular
Needs evaluation
24.04 LTS noble
Needs evaluation
23.10 mantic Ignored end of life, was needs-triage
23.04 lunar Ignored end of life, was needs-triage
22.04 LTS jammy
Needs evaluation
20.04 LTS focal
Needs evaluation
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial
Needs evaluation
14.04 LTS trusty Ignored end of standard support
libssh 24.10 oracular
Not affected
24.04 LTS noble
Not affected
23.10 mantic
Fixed 0.10.5-3ubuntu1.1
23.04 lunar
Fixed 0.10.4-2ubuntu0.2
22.04 LTS jammy
Fixed 0.9.6-2ubuntu0.22.04.2
20.04 LTS focal
Fixed 0.9.3-2ubuntu2.4
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty Ignored end of standard support
libssh2 24.10 oracular
Not affected
24.04 LTS noble
Not affected
23.10 mantic
Fixed 1.11.0-2ubuntu0.1
23.04 lunar
Not affected
22.04 LTS jammy
Not affected
20.04 LTS focal
Not affected
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty
Not affected
lxd 24.10 oracular Not in release
24.04 LTS noble Not in release
23.10 mantic Not in release
23.04 lunar Not in release
22.04 LTS jammy Not in release
20.04 LTS focal
Not affected
18.04 LTS bionic
16.04 LTS xenial
14.04 LTS trusty Not in release
openssh 24.10 oracular
Fixed 1:9.6p1-3ubuntu1
24.04 LTS noble
Fixed 1:9.6p1-3ubuntu1
23.10 mantic
Fixed 1:9.3p1-1ubuntu3.1
23.04 lunar
Fixed 1:9.0p1-1ubuntu8.6
22.04 LTS jammy
Fixed 1:8.9p1-3ubuntu0.5
20.04 LTS focal
Fixed 1:8.2p1-4ubuntu0.10
18.04 LTS bionic
16.04 LTS xenial
14.04 LTS trusty
Needs evaluation
openssh-ssh1 24.10 oracular
Needs evaluation
24.04 LTS noble
Needs evaluation
23.10 mantic Ignored end of life, was needs-triage
23.04 lunar Ignored end of life, was needs-triage
22.04 LTS jammy
Needs evaluation
20.04 LTS focal
Needs evaluation
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial Not in release
14.04 LTS trusty Not in release
paramiko 24.10 oracular
Fixed 2.12.0-2ubuntu4
24.04 LTS noble
Fixed 2.12.0-2ubuntu4
23.10 mantic
Fixed 2.12.0-2ubuntu1.23.10.2
23.04 lunar Ignored end of life
22.04 LTS jammy
Fixed 2.9.3-0ubuntu1.2
20.04 LTS focal
Fixed 2.6.0-2ubuntu0.3
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial
Needs evaluation
14.04 LTS trusty
Needs evaluation
proftpd-dfsg 24.10 oracular
Needs evaluation
24.04 LTS noble
Needs evaluation
23.10 mantic Ignored end of life, was needs-triage
23.04 lunar Ignored end of life, was needs-triage
22.04 LTS jammy
Needs evaluation
20.04 LTS focal
Needs evaluation
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial
Needs evaluation
14.04 LTS trusty Ignored end of standard support
putty 24.10 oracular
Not affected
24.04 LTS noble
Needs evaluation
23.10 mantic Ignored end of life, was needs-triage
23.04 lunar Ignored end of life, was needs-triage
22.04 LTS jammy
Needs evaluation
20.04 LTS focal
Needs evaluation
18.04 LTS bionic
Needs evaluation
16.04 LTS xenial
Needs evaluation
14.04 LTS trusty Ignored end of standard support
python-asyncssh 24.10 oracular
Fixed 2.10.1-2ubuntu1
24.04 LTS noble
Fixed 2.10.1-2ubuntu0.1
23.10 mantic Ignored end of life, was needs-triage
23.04 lunar Ignored end of life, was needs-triage
22.04 LTS jammy
20.04 LTS focal
Fixed 1.12.2-1ubuntu0.1
18.04 LTS bionic Ignored changes too intrusive
16.04 LTS xenial Ignored changes too intrusive
14.04 LTS trusty Not in release
snapd 24.10 oracular
Not affected
24.04 LTS noble
Not affected
23.10 mantic Ignored end of life, was needs-triage
23.04 lunar Ignored end of life, was needs-triage
22.04 LTS jammy
Not affected
20.04 LTS focal
Not affected
18.04 LTS bionic
Not affected
16.04 LTS xenial
Not affected
14.04 LTS trusty Ignored end of standard support

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Notes

mdeslaur

Per upstream openssh developers: While cryptographically novel, the security impact of this attack is fortunately very limited as it only allows deletion of consecutive messages, and deleting most messages at this stage of the protocol prevents user user authentication from proceeding and results in a stuck connection. The most serious identified impact is that it lets a MITM to delete the SSH2_MSG_EXT_INFO message sent before authentication starts, allowing the attacker to disable a subset of the keystroke timing obfuscation features introduced in OpenSSH 9.5. There is no other discernable impact to session secrecy or session integrity. snapd aonly uses the terminal sub-package, not the ssh part of golang-go.crypto, so it is not vulnerable

sbeattie

putty fixes include some refactoring commits that are used by the added strict kex mode support

seth-arnold

openssh-ssh1 is provided for compatibility with old devices that cannot be upgraded to modern protocols. Thus we may not provide security support for this package if doing so would prevent access to equipment.

jdstrand

snapd contains an embedded copy of golang-go.crypto lxd in 18.04 LTS and earlier contains an embedded copy of golang-go.crypto

sbeattie

proftpd-dfsg contains an ssh implementation in mod-sftp (distributed in proftpd-mod-crypto/proftpd-basic)

mdeslaur

per Debian, libssh2 older than mantic isn't vulnerable as it doesn't support ChaCha20-Poly1305 and CBC-EtM.

ccdm94

libssh will be marked as not affected for bionic and earlier as per the above note. ChaCha20-Poly1305 and CBC-EtM are present only in libssh 0.8.0 (released 2018-08-10. Bionic is version 0.8.0, but based on commit 94fa1e38, which was released 2017-08-25) and later. Patches provided by upstream do not apply cleanly to versions in bionic and earlier as several functionalities are not present in these versions of the code (making backports a more likely to introduce regressions) further supporting the defined not affected status.

Patch details

For informational purposes only. We recommend not to cherry-pick updates. How can I get the fixes?

Package Patch details
dropbear
golang-go.crypto
libssh
libssh2
openssh
paramiko
putty
python-asyncssh
snapd

Severity score breakdown

Parameter Value
Base score 5.9 · Medium
Attack vector Network
Attack complexity High
Privileges required None
User interaction None
Scope Unchanged
Confidentiality None
Integrity impact High
Availability impact None
Vector CVSS:3.1/AV:N/AC:H/PR:N/UI:N/S:U/C:N/I:H/A:N

References

Related Ubuntu Security Notices (USN)

Other references